Heating/sensing catheter appratus for minimally invasive applications

Abstract

Catheter apparatus comprises a coaxial cable having proximal and distal ends. The cable includes a hollow center conductor, an outer conductor and an electrically insulating layer between the conductors. An antenna is at the distal end of the cable, and a diplexer is connected to the cable, the diplexer including a transmit path for connecting the antenna to a transmitter which transmits first frequency signals and a receive path for connecting the antenna to a receiver which detects second frequency signals the diplexer isolating the signals on the two paths from one another. A transmission line connects the cable to the diplexer, the transmission line having a segment with a tubular inner conductor one end of which is connected to the center conductor and a second end of which is adapted for connection to a coolant source, the center and inner conductors forming a continuous coolant pathway.

What is claimed is: 
     
         1 . Catheter apparatus comprising
 an elongated flexible coaxial cable having proximal and distal ends, said cable including a hollow center conductor, an outer conductor and an electrically insulating layer in an annular space between said conductors;   an antenna at the distal end of the cable;   a diplexer including a transmit path for connecting the antenna to a transmitter which transmits signals of a first frequency and a receive path for connecting the antenna to a receiver which detects signals of a second frequency, said diplexer isolating the signals on the two paths from one another;   a transmission line connecting the cable to the diplexer, said transmission line including a segment with a tubular inner conductor one end of which is connected to the center conductor of the cable and a second end of which is adapted for connection to a coolant source, said center conductor and said inner conductor forming a continuous coolant pathway.   
     
     
         2 . The apparatus defined in  claim 1  wherein said receive path includes a first electrical filter. 
     
     
         3 . The apparatus defined in  claim 2  wherein
 said first filter comprises a waveguide with opposite ends, and said inner conductor segment extends into the waveguide adjacent one end thereof forming a tubular probe therein that connects to a dielectric conduit extending out of the waveguide thereby continuing the coolant pathway, and 
 further including a waveguide-to-cable transition adjacent the other end of the waveguide and adapted for connection to a receiver. 
 
     
     
         4 . The apparatus defined in  claim 3  wherein the transmission line is a T-shaped transmission line with a leg in said transmit path adapted for connection to a transmitter, said leg including a second electrical filter. 
     
     
         5 . The apparatus defined in  claim 3  wherein the waveguide is loaded with a dielectric material. 
     
     
         6 . The apparatus defined in  claim 3  wherein
 the diplexer includes a housing containing the transmission line and waveguide, and 
 said conduit extends from the probe to the housing exterior and includes an injection port outside the housing. 
 
     
     
         7 . The apparatus defined in  claim 1  wherein said first filter comprises a waveguide with opposite ends, and
 said transmission line includes a branch extending into the waveguide adjacent one end thereof forming a probe therein, and 
 further including a waveguide-to-cable transition adjacent the other end of the waveguide and adapted for connection to a receiver. 
 
     
     
         8 . The apparatus defined in  claim 1  and further including an impedance-matching transformer in series with the cable and the transmission line. 
     
     
         9 . The apparatus defined in  claim 1  wherein the cable outer conductor comprises braided conductive strands. 
     
     
         10 . The apparatus defined in  claim 1  wherein the cable insulating layer comprises a flexible winding of one or more dielectric strands having multiple fluid flow paths therebetween. 
     
     
         11 . The apparatus defined in  claim 1  wherein said antenna comprises an extension of the center conductor beyond the outer conductor and the insulating layer. 
     
     
         12 . The apparatus defined in  claim 11  wherein said extension is tubular and continues said fluid pathway to the outside. 
     
     
         13 . The apparatus defined in  claim 1  wherein said antenna is connected to the center conductor via a connection device at the distal end of the cable. 
     
     
         14 . The apparatus defined in  claim 13  wherein the connection device defines a fluid path between the interior of the center conductor and the outside. 
     
     
         15 . The apparatus defined in  claim 13  wherein the connection device defines a fluid passage between the interior of the center conductor and said annular space so that said annular space can provide a coolant return path along the cable. 
     
     
         16 . The apparatus defined in  claim 1  wherein the antenna is flexible. 
     
     
         17 . The apparatus defined in  claim 1  and further including a stand-off device adjacent to the distal end of the cable for centering said antenna in a body passage. 
     
     
         18 . The apparatus defined in  claim 1  and further including one or more temperature detectors positioned in said fluid pathway for monitoring coolant temperature at one or more locations therealong. 
     
     
         19 . The apparatus defined in  claim 1  and further including a device for introducing an x-ray contrast agent into said center conductor. 
     
     
         20 . The apparatus defined in  claim 1  and further including a microwave or RF transmitter connected to said transmit path. 
     
     
         21 . The apparatus defined in  claim 1  and further including a coolant source connected to said second end of the tubular inner conductor of said transmission line segment. 
     
     
         22 . Catheter apparatus comprising an elongated flexible coaxial cable having proximal and distal ends, said cable including
 a hollow center conductor;   an outer conductor, and   an electrical insulating layer in an annular space between said conductors, said insulating layer being constituted by one or more windings of a dielectric material defining multiple flow paths along said annular space, and   
     
     
         23 . The apparatus defined in  claim 22  and further including a connection device at the distal end of the cable connecting the interior of the center conductor to said annular space so that when a gaseous coolant is flowed into the proximal end of the cable, the coolant travels along the center conductor to the distal end of the cable and exhausts from the cable via said connection device and flow paths thereby cooling the center conductor. 
     
     
         24 . The apparatus defined in  claim 23  wherein the connection device comprises a closed hollow end cap secured to the distal end of the cable and which connects the interior of the center conductor to said annular space. 
     
     
         25 . The apparatus defined in  claim 24  wherein the center conductor extends into said cap to form an antenna. 
     
     
         26 . The apparatus defined in  claim 23  wherein the connection device comprises a bead in the annular space at the distal end of the cable, said bead defining a passage between the interior of the center conductor and the annular space. 
     
     
         27 . The apparatus defined in  claim 22  wherein the center conductor extends beyond the outer conductor at the distal end of the cable to form an antenna. 
     
     
         28 . The apparatus defined in  claim 27  and further including a stand-off device adjacent to the distal end of the cable for centering the antenna in a body passage. 
     
     
         29 . The apparatus defined in  claim 27  and further including a diplexer connected to the cable, said diplexer including a transmit path for connecting the antenna to a transmitter which transmits signals of a first frequency and a receive path for connecting the antenna to a receiver which detects signals of a second frequency, said diplexer being designed to isolate the signals on the two paths from one another. 
     
     
         30 . The apparatus defined in  claim 29  and further including an impedance-matching transformer in series between the cable and the diplexer. 
     
     
         31 . The apparatus defined in  claim 29  wherein said transmit path and said receive path are comprised of a T-shaped transmission line which is arranged and adapted to provide both a coolant path between a coolant source and said center conductor and an impedance matching transformer. 
     
     
         32 . The apparatus defined in  claim 29  wherein said cable and said diplexer are formed as a unitary disposable first part designed for connection both electrically and mechanically to a mating reusable second part containing microwave receiver. 
     
     
         33 . The apparatus defined in  claim 22  wherein said outer conductor comprises braided conductive strands. 
     
     
         34 . The apparatus defined in  claim 22  and further including one or more temperature sensors in said center conductor.